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PubMed1998

Alkaline phosphatase (EC 3.1.3.1) in serum is inhibited by physiological concentrations of inorganic phosphate.

Natural and artificial manipulation of tissue nonspecific alkaline phosphatase activity indicates that pyrophosphate, phosphoethanolamine, and pyridoxal 5'-phosphate are among the natural substrates for this enzyme. Although inorganic phosphate has been recognized as a competitive inhibitor of this enzyme for many years, the influence of phosphate on alkaline phosphatase activity in serum under physiological conditions has not been previously reported. We examined the kinetics of tissue nonspecific alkaline phosphatase from bovine kidney and sera from 49 patients with a wide range of endogenous phosphate concentrations using pyridoxine 5'-phosphate as a substrate at pH 7.4. For the bovine kidney enzyme, the Km was 0.42 +/- 0.04 micromol/L, and the Ki for phosphate was 2.4 +/- 0.2 micromol/L. Analysis of the kinetics using pyridoxine 5'-phosphate in undiluted serum from 10 subjects with phosphorus ranging from 0.5-2.1 mmol/L and alkaline phosphatase activity ranging from 41-165 nmol/min x mL gave estimates for the Km of 56 +/- 11 micromol/L and for the Ki of 540 +/- 82 micromol/L for phosphate. This indicates that under physiological conditions alkaline phosphatase activity toward pyridoxine 5'-phosphate is reduced approximately 50% by the normal phosphate concentration and that it will increase or decrease significantly in response to changes in phosphate concentration within the ranges observed clinically.

Adult↗
PubMed1988

Symptomatic sclerosing cholangitis in patients with a normal alkaline phosphatase: two case reports and a review of the literature.

The diagnosis of sclerosing cholangitis is usually not considered in the absence of an elevation of serum alkaline phosphatase. The purpose of this paper is to report two symptomatic cases of primary sclerosing cholangitis (PSC) which presented with a normal alkaline phosphatase, and to review the literature regarding alkaline phosphatase in PSC. A total of 172 patients with PSC were identified in the literature; six of these patients (3%) presented with a normal alkaline phosphatase. Patients with diseases known to be associated with primary sclerosing cholangitis and having a compatible clinical presentation should be considered for evaluation with endoscopic retrograde cholangiography, even in the presence of a normal level of serum alkaline phosphatase.

Adult↗
PubMedDate not supplied

Osteocalcin and bone alkaline phosphatase in the serum of women with liver disease.

To identify the types of liver disease in which osteopenia is a prominent feature and to understand the mechanisms of bone loss, bone mineral density was measured in the lumbar spine and hip, bone alkaline phosphatase, osteocalcin, and biochemical markers of calcium homeostasis were measured in 42 women, aged 33 to 52, with chronic liver disease and in 299 healthy women of similar age. In control women, bone alkaline phosphatase and osteocalcin correlated negatively with bone density at all sites (p less than 0.05). In women with liver disease, osteocalcin correlated negatively with bone density in the lumbar spine (p less than 0.007), whereas bone alkaline phosphatase did not correlate with bone density at any site. Bone alkaline phosphatase correlated positively with osteocalcin in control women (p = 0.001) and negatively with osteocalcin in women with liver disease (p = 0.03). Serum bone alkaline phosphatase in women with liver disease was increased significantly over serum bone alkaline phosphatase of control women, probably because of decreased clearance owing to defective function or decreased numbers of hepatic asialoglycoprotein receptors. Bone density was lower in the lumbar spines and hips of women with primary sclerosing cholangitis, primary biliary cirrhosis, and chronic active hepatitis or fibrosis without cirrhosis than in the lumbar spine and hips of control women. However, the differences were not significant, possibly because of the small sample size. It is concluded that, in liver disease, osteocalcin is a more reliable marker of osteoblastic function than bone alkaline phosphatase. Although our results show that bone density may decrease in women with cholestatic liver disease, larger studies are needed to determine the degree of osteopenia.

Adult↗
PubMed1975

Immunological methods for human placental alkaline phosphatase (Regan isoenzyme).

Four different immunological methods for the determination of the placental isoenzyme of alkaline phosphatase (Regan isoenzyme) were compared in 64 normal blood donors, 23 healthy laboratory and medical staff workers and 68 pregnant women: a. Inhibition by soluble antibodies to the placental enzyme. b. Precipitation with soluble antibodies. c. Precipitation with immobilized antibodies. d. Measurement of the activity of the placental alkaline phosphatase following binding to an immunoabsorbent that has been obtained by polymerization of anti-placental-alkaline phosphatase gamma-globulin using glutaraldehyde. The immunoabsorbent method yielded the best results. The optimal conditions were evaluated for the measurement of the activity of immunoabsorbent-fixed placental (tumoral) alkaline phosphatase activity. This method was applied to 209 normal blood donors and to 239 patients with different malignant tumors: 25.5 percent of the cancer patients exhibited an elevated Regan -isoenzyme activity in the serum.

Alkaline Phosphatase↗
PubMed1989

Preventive effects of zinc on cadmium-induced inhibition of alkaline phosphatase activity and mineralization activity in osteoblast-like cells, MC3T3-E1.

In order to determine the specific action of cadmium on bone metabolism, the effect of cadmium on alkaline phosphatase activity, a marker enzyme of osteoblasts, was compared with that of other divalent heavy metal ions, i.e., zinc, manganese, lead, copper, nickel and mercury (10 microM each), using cloned osteoblast-like cells, MC3T3-E1. Cadmium had the strongest inhibitory effect on alkaline phosphatase activity of the cells among the metals tested. At the same dose, however, cadmium failed to inhibit cellular glucose-6-phosphatase and lactate dehydrogenase activities, suggesting that the inhibitory effect of cadmium on alkaline phosphatase was specific and was not dependent on cell injury. Cadmium treatment caused a significant decrease in cellular zinc level, but mercury treatment had no such effect at the dose inhibiting alkaline phosphatase activity. There was a good correlation between decrease of cellular zinc level and inhibition of alkaline phosphatase activity in cadmium-treated cells. Concomitant treatment of the cells with zinc prevented the cadmium-induced inhibition of alkaline phosphatase activity. However, this was not the case in the mercury-induced inhibition. Cadmium also inhibited the mineralization of osteoblasts. When 10 or 20 microM zinc was concomitantly added to the cultures, the inhibition of mineralization was prevented. These data suggest that the inhibitory effect of cadmium in osteoblasts may be closely related to its influence on the cellular zinc metabolism.

Alkaline Phosphatase↗
PubMed1998

Purification and characterization of alkaline phosphatase containing phosphotyrosyl phosphatase activity from the bacterium Prevotella intermedia.

A novel alkaline phosphatase, designated PiALP, has been purified and characterized from Prevotella intermedia ATCC 25611, an anaerobe implicated in progressive periodontal disease. The enzyme was a homodimer of apparently identical subunits of Mr 54 kDa. Thiol-reducing agents completely inhibited the purified enzyme. The enzyme was highly stable even at 80 degrees C. It exhibited substantial activity against tyrosine-phosphate-containing Raytide. The phosphatase activity was sensitive to orthovanadate and Zn2+ but highly resistant to okadaic acid. The amino acid sequence of peptides derived from PiALP showed a high degree of identity (65%) with alkaline phosphatases from Zymomonas mobilis and Synechococcus. The present results imply that PiALP might represent a new family of alkaline phosphotyrosyl phosphatases which has not been described previously.

Alkaline Phosphatase↗
PubMed1975

Inhibition studies of alkaline phosphatase in hard tissue-forming cells.

The effects of the alkaline phosphatase inhibitors levamisole and R 8231 on p-nitro-phenylphosphatase, inorganic pyrophosphatase and adenosine triphosphatase (ATPase) activities in dentingenically active odontoblasts were studied. The p-nitrophenylphosphatase and inorganic pyrophosphatase activities were inhibited, while 40% of the ATP-splitting enzyme activity remained under the assay condition used. This finding, togeather with earlier studies, indicates that at least two different phosphatase are active at alkaline pH in hard tissue-forming cells; on nonspecific alkaline phosphatase and one specific ATPase. The ATPase activity is uninfluenced by ouabain and ruthenium red and is activated by Ca-2+ ions.

4-Nitrophenylphosphatase↗
PubMed1993

Differential expression of alkaline phosphatase in clones of human osteoblast-like cells.

We established cultures of cells growing out from adult bone chips and maintained them through 12 passages in culture. The cultures showed osteoblastic phenotype accompanied by synthesis of collagen type I, osteonectin, alkaline phosphatase, and osteocalcin. We report the characterization of 21 clones obtained from three different individual primary cultures. We studied the expression of osteonectin, alkaline phosphatase, collagen, and osteocalcin in the clones. Metabolic labeling showed production of type I collagen and of osteonectin in all clones studied. In two-thirds of the clones and in mass cultures alkaline phosphatase was not detected at passage 2, but it was detected in increasing amounts at later passages in culture. The clones attained different but detectable levels of expression of this marker by passage 8. The different levels in the expression of alkaline phosphatase in positive clones may be because they were derived from cells at different stages of osteoblastic maturation or due to small changes in microenvironment. The alkaline phosphatase-positive clones were tested for osteocalcin, and they showed measurable expression only at passage 10. A third of the clones obtained were negative for alkaline phosphatase during 12 passages in culture. The obtainment of clones unable to produce alkaline phosphatase may be due to loss of differentiating potential under the in vitro culture conditions. The growth rate and potential of all clones studied were similar through 12 passages in culture, regardless of their potential for expression of alkaline phosphatase.

Adult↗
PubMed1992

Caco-2 cell transfection by rat intestinal alkaline phosphatase cDNA increases surfactant-like particles.

The rat enterocyte produces a particle with surfactant-like properties (including a whorled appearance, enrichment for dipalmitoyl phosphatidylcholine, and ability to lower surface tension) that also is enriched for intestinal alkaline phosphatase. Human Caco-2 cells grown on polycarbonate filters were utilized to study the secretion of these particles and exhibited whorls and strands of unilamellar membranes, particularly concentrated at the apical pole or near junctional complexes. Concentrated culture medium from these cells separated on continuous NaBr gradients revealed a fraction at density = 1.07 g/l enriched for phosphatidylcholine and intestinal alkaline phosphatase. This fraction contained membranous sheets containing alkaline phosphatase, detected by immunolocalization. Phosphatidylcholine comprised 54% of phospholipid in this fraction, compared with 20% in brush borders. When Caco-2 cells were transfected with cDNA encoding rat intestinal alkaline phosphatase, cellular phosphatase activity increased twofold, but activity in the medium increased 14-fold to > 200 (average 32)-fold. Ultrastructurally, compared with mock-transfected cells or cells transfected with human placental alkaline phosphatase, transfection with rat intestinal alkaline phosphatase cDNA led to intracellular and extracellular accumulation of surfactant-like particles. We conclude that surfactant-like particles are produced by Caco-2 cells, and their production can be enhanced by transfection with a cDNA encoding a protein known to be associated with such particles.

Alkaline Phosphatase↗
PubMed1995

Tissue-nonspecific alkaline phosphatase participates in the establishment and growth of feather germs in embryonic chick skin cultures.

Alkaline phosphatase activity is present in the mesoderm of embryonic chick skin and becomes spatially restricted to the dermal condensation of the developing feather germs. Inhibitors to tissue-nonspecific (liver/bone/kidney), but not intestinal alkaline phosphatase inhibit the establishment and growth of feather germs in cultured skins. A window of maximum sensitivity to the inhibitor was observed to be the first day of culture when early development and establishment of pattern takes place. The cDNA for the avian tissue-nonspecific alkaline phosphatase was cloned and sequenced, and Southern analysis revealed a single copy of this gene in the avian genome. Northern analysis revealed that a 2.8 kb transcript for this form of alkaline phosphatase is present in developing skin.

Alkaline Phosphatase↗
PubMed1980

Inhibition of alkaline phosphatase by several diuretics.

Acetazolamide, furosemide, ethacrynic acid and chlorothiazide, diuretics of considerable structural diversity, inhibit alkaline phosphatase. The inhibition is reversible and the mechanism is of the mixed type, having both competitive and non-competitive characteristics. Ki is calculated to be 8.4, 7.0, 2.8 and 0.1 mmol/l for acetazolamide, furosemide, ethacrynic acid and chlorothiazide, respectively. Chlorothiazide is a much more potent inhibitor of alkaline phosphatase than the other three diuretics. The combination of ethacrynic acid and cysteine, itself an alkaline phosphatase inhibitor, is less inhibitory than ethacrynic acid alone. Rat and human kidney alkaline phosphatase are equally sensitive to chlorothiazide, ethacrynic acid and furosemide.

Acetazolamide↗
PubMed2001

Activation of p44/p42 mitogen-activated protein kinase limits triiodothyronine-stimulated alkaline phosphatase activity in osteoblasts.

It has been shown that thyroid hormone stimulates the activity of alkaline phosphatase, a marker of mature osteoblast phenotype, in osteoblasts. In the present study, we investigated whether p44/p42 mitogen-activated protein (MAP) kinase is involved in the thyroid hormone-stimulated alkaline phosphatase activity in osteoblast-like MC3T3-E1 cells. Triiodothyronine (T(3)) markedly induced the phosphorylation of p44/p42 MAP kinase. PD98059 and U0126, inhibitors of the upstream kinase that activates p44/p42 MAP kinase, significantly enhanced the T(3)-induced alkaline phosphatase activity in a dose-dependent manner. The phosphorylation of p44/p42 MAP kinase induced by T(3) was reduced by U0126. These results strongly suggest that p44/p42 MAP kinase takes part in the thyroid hormone-stimulated alkaline phosphatase activity in osteoblasts and that p44/p42 MAP kinase plays an inhibitory role in the thyroid hormone-effect.

3T3 Cells↗
PubMed1963

The value of leucocyte alkaline phosphatase determinations in the diagnosis of ectopic pregnancy.

Leucocyte alkaline phosphatase activity has been determined in a normal group, a group of pregnant patients, and a group of patients with ectopic pregnancy.A great rise in alkaline phosphatase occurred in pregnant patients in their third trimester, but the results were only slightly raised in the ectopic group. Five of six consecutive cases gave results which fell within the normal range. The method is not considered to be of value in the diagnosis of ectopic pregnancy.

Alkaline Phosphatase↗
PubMedDate not supplied

Alkaline phosphatases as reporters of developmental and cancerous events.

Alkaline phosphatases comprise a family of isozymes whose expression is associated with important oncodevelopmental events. This presentation summarizes the relationship between alkaline phosphatase isozyme expression and specific developmental and disease processes, including malignancy. Several experimentally testable hypothesis are proposed that should help clarify the significance of these disease associations and the in vivo function of this interesting group of molecules.

Alkaline Phosphatase↗
PubMed1981

1,25-Dihydroxyvitamin D3 stimulates the alkaline phosphatase activity of osteoblast-like cells.

Rat osteogenic sarcoma cells which have osteoblast properties including the ability to form bone and to mineralize were recently found to possess specific cytoplasmic receptors for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). We have examined now the effect of 1,25(OH)2D3 and other vitamin D3 metabolites on the alkaline phosphatase of such cell lines. We found in two cell lines cultured in the presence of 10(-7) M 1,25(OH)2D3 a 3-fold increase in intracellular alkaline phosphatase activity and a 6-fold increase in secreted alkaline phosphatase activity. The cellular response occurred in a dose-dependent fashion at a range of 10(-9) to 10(-7) M. In a third cell line, which does not possess the specific receptor for 1,25(OH)2D3, we could not detect stimulation of alkaline phosphatase. Vitamin D3, 25-dihydroxyvitamin D3, and 24,25-dihydroxyvitamin D3 at 10(-7) M had no effect on alkaline phosphatase. The effect of 1,25(OH)2D3 was enhanced in the presence of increased calcium. In view of the postulated role for alkaline phosphatase in calcification, we speculate that the stimulatory effect of 1,25(OH)2D3 on the alkaline phosphatase activity of osteoblast-like cells indicates a direct involvement of 1,25(OH)2D3 in bone mineralization.

Alkaline Phosphatase↗
PubMed1979

Expression of KB cell alkaline phosphatase isoenzymes during growth in immunosuppressed LEW rats.

Alkaline phosphatase isoenzyme expression of human tumor xenografts was studied by the growing of KB cells in immunosuppressed neonatal LEW rats. In culture these cells produced the oncoamniotic (FL) isoenzyme as the major form and the Regan isoenzyme as a minor fraction as well as a "hybrid" that shared properties of both of the other isoenzymes. Despite a reduction in specific activity, this isoenzyme pattern was essentially unchanged during in vivo growth. KB cells "pretreated" in culture with the glucocorticoid prednisolone in hyperosmolal medium exhibited a decrease in the levels of the oncoamniotic (FL) isoenzyme and an increase in the Regan isoenzyme. During growth of pretreated cells in vivo, a time-dependent resumption in the expression of the oncoamniotic (FL) isoenzyme was associated with the disappearance of the Regan isoenzyme. This shows that the expression of the oncoamniotic (FL) isoenzyme is not restricted to human tumor cells monophenotypic with respect to alkaline phosphatase.

Alkaline Phosphatase↗
PubMed1993

Postcholestatic alkaline phosphatase activity after relief of bile duct obstruction in the rat.

The effects of obstructive cholestasis on the activity of alkaline phosphatase have been extensively studied in serum and liver tissue. However, very little is known about the activity of this enzyme in the postcholestatic condition after relief of the biliary obstruction. The purpose of this study has been to characterize alkaline phosphatase activity in serum, liver and bile in the postcholestatic period and to relate it to changes in bile acid secretory rate. Serum activity and biliary secretory rates of alkaline phosphatase were markedly increased in rats subjected to a reversible obstructive cholestasis for 24 hr or 48 hr and progressively declined along the postcholestatic period to values not significantly different from those of control rats within 48 hr. A significant direct linear relationship between the biliary secretory rates of enzyme activity and bile salts was apparent both in cholestatic groups and in the control groups. The slope of the regression line (units of alkaline phosphatase secreted per micromole of bile salts) was 1.5-fold to 3-fold higher in cholestatic animals. Remarkably, a positive y-intercept of regression lines suggested that a significant fraction of the enzyme was secreted independently of bile salts; this fraction was 18-fold and 34-fold greater in 24-hr and 48 hr cholestatic rats, respectively, compared with that in controls. Sodium taurocholate administered intravenously, either as a bolus or as an infusion at increasing submaximal rates, resulted in parallel increases of bile salt and alkaline phosphatase secretory rates into bile. The enzyme activity secreted per micromole of taurocholate was significantly greater in cholestatic than in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1979

Influence of chronic Cd intoxication on the alkaline phosphatase activity of liver and kidney; biochemical, histochemical and histological investigations.

To distinguish between: (a) the decrease of activity of alkaline phosphatase due to inhibition by cadmium; and (b) the decline of enzyme activity due to cell destruction, 20 adult female Wistar rats were treated 3 times/week with 0.5 mg/kg CdCl2 (by subcutaneous injection) during 28 weeks. Controls received the same volume of 0.9% NaCl solution. The animals were killed at different intervals. The liver and kidneys were investigated with biochemical, histochemical, light and electron microscopical techniques. The liver homogenates show an increase of alkaline phosphatase activity after about 12-13 weeks, whereas the activity of this enzyme in the kidney decreases. This activity could not be restored by the administration of Zn ions to the medium of the enzyme assay. However, in previous in vitro experiments the Cd inhibited alkaline phosphatase activity could be totally restored by such a Zn administration. By histochemical assay of alkaline phosphatase in the renal cortex a decrease of enzyme activity was demonstrated. By evaluation of the results obtained with light and electron microscopy, in combination with the biochemical results, the decrease of alkaline phosphatase activity in the kidney should be considered as a real decrease in the amount of this enzyme due to cell degeneration.

Acetylglucosaminidase↗